The invention relates to plant disease resistance.
Plant diseases cause crop losses that are devastating to world food supply and human well being. Plants have evolved defense mechanisms to ward off diverse biotic attacks to ensure their survival and fitness. This plant immunity occurs at multiple levels and can be largely divided into two branches (1, 31). One is a general resistance responding to molecules common to many pathogens and the other is a ‘cultivar-specific’ resistance responding to pathogen virulent factors. The latter resistance is induced upon a specific recognition of the pathogen race-specific avirulence (Avr) gene by the disease resistance (R) gene of the host plant (32). This ‘gene-for-gene’ interaction leads to rapid and efficient defense responses including a form of programmed cell death named hypersensitive response (HR) to restrict the growth of pathogens (33). A number of R genes have been molecularly cloned in many species and the largest class of R proteins contains ‘nucleotide-binding’ (NB) and leucine-rich repeat (LRR) domains (8, 9). A direct or indirect interaction between Avr proteins and the R proteins activates downstream signaling events leading to local HR and systemic acquired resistance throughout plants.
Plant defense responses are modulated by a number of environmental factors including light, humidity, and temperature. Temperature variations influence disease resistance to bacteria, fungi, virus, and insects (34). A high temperature often suppresses disease resistance in plants, and this phenomenon is named ‘heat masking’. This heat sensitivity has been reported in a number of disease resistance responses mediated by R genes such as the N gene in tobacco (35), Mi in tomato (6), RPW8 in Arabidopsis (36), and SNC1 in Arabidopsis (7).
There is accordingly a need in the art for plants having increased tolerance to temperature thereby avoiding high temperature-suppression of a resistance response. Genes conferring temperature insensitivity are consequently needed for disease resistance management at high temperatures. The present invention provides such genes and includes methods for conferring disease resistance to plants at temperatures at which defense responses are typically diminished or masked due to heat sensitivity.